LTE transmission mask adjustment to maximize performance and reduce interference

ABSTRACT

System and methods for using channel quality reports to reduce inter-band interference are disclosed. Channel information is received at a first wireless communication device from a second wireless communication device. The first wireless device is operating in a first frequency range, and the second wireless device is operating in a second frequency range. The first frequency range is adjacent to the second frequency range. A channel quality report is generated at the first wireless communication device. The channel quality report indicates that particular sub-bands in the first frequency range have low channel quality. The particular sub-bands are selected using the channel information.

BACKGROUND

The Industrial, Scientific and Medical (ISM) radio bands includeportions of the radio spectrum that are reserved internationally for theuse of radio frequency (RF) transmissions for industrial, scientific andmedical purposes. Generally, there is no regulatory protection from ISMdevice operation and equipment operating in the ISM bands must tolerateany interference generated by ISM equipment. Although these bands wereoriginally not intended for telecommunications, in recent years the ISMbands have been used for short-range, low power communications systems,such as cordless phones, Bluetooth devices, near field communication(NFC) devices, and wireless computer networks, that use frequencies inthe ISM band as well as other frequencies allocated to low powercommunications.

For example, the IEEE 802.11 Wi-Fi standards identify the channels thatmay be used for a Wireless Local Area Network (WLAN). The 2.4 GHz ISMband is from 2400 MHz-2500 MHz. There are fourteen channels defined foruse by 802.11 Wi-Fi for the 2.4 GHz ISM band. These 802.11 channels span2402 MHz-2483 MHz. 802.11 Wi-Fi is adapted for use within unlicensedspectrum, which enables users to access the radio spectrum without theneed for the regulations and restrictions; however this spectrum is alsoshared by many other users and is exposed to interference.

Devices using the Bluetooth wireless technology standard also operate inthe 2.4 GHz ISM band at 2.4 GHz-2.485 GHz. Bluetooth devices are used inshort-range personal area networks. To reduce interference with otherprotocols that use the 2.4 GHz ISM band, the Bluetooth protocol dividesthe band into seventy-nine channels and changes channels many times persecond. Bluetooth devices may also detect existing signals in the ISMband and attempt to avoid them by negotiating a channel map with otherBluetooth devices.

Long Term Evolution (LTE) cellular networks operate in a number ofassigned bands, including the bands 2300 MHz-2400 MHz and 2500 MHz-2690MHz, which are adjacent to both sides of the ISM band.

The transmissions by each of these systems cause interferences to theother systems' reception. Additionally, intermodulation causesdegradation of the LTE transmission links.

SUMMARY

Embodiments of the invention provide systems and methods for usingchannel quality reports to reduce inter-band interference according toone embodiment. Channel information is received at a first wirelesscommunication device from a second wireless communication device. Thefirst wireless device is operating in a first frequency range, and thesecond wireless device is operating in a second frequency range. Thefirst frequency range is adjacent to the second frequency range. Achannel quality report is generated at the first wireless communicationdevice. The channel quality report indicates that particular sub-bandsin the first frequency range have low channel quality. The particularsub-bands are selected using the channel information.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, wherein:

FIG. 1 is a block diagram of a system implementing one embodiment.

FIG. 2 illustrates channels within an ISM band and LTE sub-bands.

FIG. 3 illustrates the change in spectral emissions in the ISM bandfrequencies for different CQI reports.

FIG. 4 illustrates an alternative embodiment in which an LTE transceiverand an ISM band transceiver are in different devices.

FIG. 5 is a block diagram illustrating internal details of a mobile UEand a base station, such as an LTE eNodeB, operating in a networksystem.

FIG. 6 is a flowchart illustrating a method for using channel qualityreports to reduce inter-band interference according to one embodiment.

DETAILED DESCRIPTION

The invention now will be described more fully hereinafter withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Oneskilled in the art may be able to use the various embodiments of theinvention.

When an LTE base station (eNodeB) or user equipment (UE) transmits onfrequencies in the sub-bands that are adjacent to the ISM band, the LTEemissions significantly degrade WLAN and Bluetooth reception. Similarly,the WLAN and Bluetooth transmissions in the ISM band can degradeadjacent LTE sub-bands. The degradation is reflected in reduction ofreceiver sensitivity level and the maximum possible range between thetransmitter and receiver of the degraded technology.

In a prior solution, this problem was addressed with a time domainsolution that defines time slots for transmission by Bluetooth and WLANdevices. In this solution, the LTE devices avoid transmissions in thetimeslots that are assigned to Bluetooth and WLAN devices. Similarly,other timeslots may be assigned to LTE devices and designated foravoidance by Bluetooth and WLAN devices. This solution has significantdisadvantages because it reduces network capacity and bandwidth for theLTE network and degrades system performance for the effected Bluetoothand WLAN devices. The time domain solution is overly complicated andreduces the available transmission times for one of the systems whiledrastically degrading network performance.

Another possible solution uses analog filtering to provide a high levelof isolation in adjacent bands. The degree of isolation required to makethis effective (e.g., approximately 60 dB at 20 MHz away from the passband) is currently not possible. Even the best RF filters available arenot capable of providing enough RF isolation

Embodiments described herein provide a solution that applies to bothFrequency-Division Duplexing (FDD) and Time-Division Duplexing (TDD) LTEtechnologies while improving both WLAN and Bluetooth networks. LTEChannel Quality Indication (CQI) reports from UEs to the eNodeB are usedto reduce transmissions in the sub-bands that are adjacent to the ISMband and thereby reduce emissions into both the ISM and LTE band. Thenumber of sub-bands reported via CQI may be determined based upon thebandwidth size that has been interrupted over the ISM band. Such asolution is simple to apply and does not require any protocol or designchanges to apply to both FDD and TDD LTE technologies.

FIG. 1 is a block diagram of a system implementing one embodiment. Userequipment (UE) device 101 is capable of transmitting on both LTE bandsand ISM bands. LTE transceiver 102 is used to generate and transmitsignals on LTE channels to LTE eNodeB 103. LTE transceiver 102 alsoprocesses signals received on LTE channels from LTE eNodeB 103. LTEeNodeB 103 directs which sub-bands are used by LTE device 101. Device101 sends periodic and/or aperiodic CQI reports to eNodeB 103. The CQIreports tell the eNodeB scheduler what data rate the UE expects to beable to receive and are used by the eNodeB 103 to assign sub-bands to UEdevice 101.

The periodic CQI report is carried by the Physical Uplink ControlChannel (PUCCH). But if UE device 101 needs to send uplink (UL) data inthe same subframe as a scheduled periodic CQI report, the periodic CQIreport will use the Physical Uplink Shared Channel (PUSCH) together withthe UL data transmission since the UE cannot transmit on both PUCCH andPUSCH simultaneously. In order to get a more detailed CQI report, eNodeB103 can trigger an aperiodic CQI report when needed. The aperiodic CQIreport is transmitted on PUSCH, either alone or together with UL data.

The CQI report can be divided into three levels: wideband, UE-selectedsubband, and higher layer configured subband. The wideband reportprovides one CQI value for the entire downlink system bandwidth. TheUE-selected subband CQI report divides the system bandwidth intomultiple subbands, selects a set of preferred subbands (the best Msubbands), then reports one CQI value for the wideband and onedifferential CQI value for the set (assume transmission only over theselected M subbands). The higher layer configured subband reportprovides the highest granularity. It divides the entire system bandwidthinto multiple subbands, then reports one wideband CQI value and multipledifferential CQI values, one for each subband.

UE device 101 also includes an ISM band transceiver 104 forcommunication with other ISM band devices 105. The ISM band transceiver104 and ISM band device 105 may communicate using the Bluetooth standardor the IEEE 802.11 WiFi standard, for example. Communication in the ISMband may use any other appropriate standard, such as the ZigBeeprotocol, the IEEE 802.15 standard, or any other standard or protocolsupporting Wireless Personal Area Networks (WPANs) or WLANs.

LTE transceiver 102 and ISM band transceiver 104 may be differentchipsets in the same UE device 101, for example. UE device 101 alsoincludes a controller 106, which may be a microprocessor based devicefor controlling the operation of the LTE transceiver 102 and ISM bandtransceiver 104. Controller 106 may monitor what bands/sub-bands areassigned to UE device 101 and measure interference on assignedbands/sub-bands and adjacent bands. For example, referring to FIG. 2, UEdevice 101 may communicate with ISM device 105 on assigned channelswithin ISM band 201. UE device 101 may also be assigned to use one ormore LTE sub-bands 202-206 for uplink and downlink communications withLTE eNodeB 103.

Controller 106 and ISM band transceiver in UE device 101 may monitor anddetect noise and channel degradation in the ISM band that is caused byLTE transmissions in adjacent sub-bands. By reshaping the LTEtransmissions, the noise level in the ISM band may be reducedsufficiently to allow full performance of ISM band device 105, such as aWLAN and Bluetooth device, without degrading LTE performance.

UE device 101 can take into account the degradation on the ISM adjacentchannel when generating CQI reports to LTE eNodeB 103. UE device 101uses sub-band CQI reports to eNodeB 103 to reflect bad channelconditions on the sub-bands 202-206 adjacent to ISM band 201. As aresult, LTE eNodeB 103 will avoid scheduling the adjacent sub-band andmutual interference will be significantly degraded. For example, the UEdevice 101 may report poor CQI for the sub-bands that are needed by ISMband devices. Knowing the channel being used by the ISM band transceiver104, the UE device 101 may calculate the degradation caused bytransmissions on adjacent LTE sub-band and generate CQI reports thatindicate the sub-bands should be avoided. The eNodeB 103 will respond byassigning other non-adjacent sub-bands to UE device 101.

The CQI report can be correlated to feedback from ISM band device 105and/or ISM band transceiver 104 regarding the severity and degradationin ISM system performance. In one embodiment, the reports range from 1to 4, wherein a level 1 request corresponds to a reduction of 4 MHz inthe adjacent LTE band. This is equivalent to moving the LTE transmissiontwenty-four Resource Blocks (RB) away from the ISM band and increasingspectral isolation.

FIG. 3 illustrates the change in spectral emissions 301-305 in the ISMband frequencies 306 for different CQI reports. Traces 301-305 areexamples of the sums of interfering LTE transmissions from adjacentsub-bands. Channel 307 represents a 20 MHz WLAN channel, for example. Asillustrated, the LTE transmissions 301 from adjacent sub-bands exceed−40 dBm are degrading the WLAN channel 307. A WLAN device, such as ISMdevice 105, or an ISM band transceiver 104 may detect this LTEinterference in channel 307 and notify a UE device, such as device 101.UE device 101 generates a CQI report that will result in the LTE eNodeBassigning LTE sub-bands that will minimize the degradation of WLANchannel 307. Initially, the LTE transmission without CQI adjustments 301may cause interference in WLAN channel 307. That interference isminimized by the UE device sending CQI reports that cause the eNodeB toavoid adjacent LTE sub-bands. In the case where a CQI level-4 report issent, the LTE transmission 305 is reduced to below −40 dBm in the WLANchannel 307.

The LTE emissions into the ISM band are reduced by shaping the LTEtransmission. This allows uninterrupted receive time for the ISM bandusers. This technique allows the LTE and ISM band systems to allachieving full system performance without influencing downlink bandwidthof the LTE network. The CQI report method of reducing emissions in theISM band can be implemented protocol changes to any of the systems.

FIG. 4 illustrates an alternative embodiment in which an LTE transceiver401 and an ISM band transceiver 402 are in different devices. LTE UEdevice 403 includes LTE transceiver 401 and controller 404. LTE UEdevice 403 communicates with LTE eNodeB base station 405 on assigned LTEsub-bands.

ISM band UE device 406 includes ISM band transceiver 402 and controller407. ISM band UE device 406 communicates with other ISM band devices408, such as Bluetooth, WiFi, or ZigBee devices, using channels assignedin the ISM band.

Although LTE transceiver 401 and ISM band transceiver 402 are indifferent UE devices 403, 406, they may communicate channel interferenceinformation between them over a separate link 409. In one embodiment,controllers 404 and 407 communicate over link 409 to exchange channelassignment and/or channel degradation information. Link 409 may be anywireless or wired connection between devices 403 and 406 that allows LTEUE device 403 to receive channel information from ISM UE device 406. LTEUE device 403 then uses the channel information to generate CQI reportsthat will cause LTE eNodeB 405 to assign sub-bands adjacent to the ISMband in a manner that minimizes interference.

Although the examples used herein refer to the ISM band, it will beunderstood that the present invention is frequency-band agnostic andapplies to any frequency band. For example, proposals for LTE Advancedin unlicensed spectrum (LTE-U) suggest that both LTE systems and WiFiWLANs would operate in the 5 GHz unlicensed band. The present inventionmay be used to minimize interference between WLANs operating in the 5GHz unlicensed band and LTE UEs operating in the 5 GHz unlicensed bandor in adjacent bands.

FIG. 5 is a block diagram illustrating internal details of a mobile UE501 and a base station 503, such as an LTE eNodeB, operating in anetwork system. Mobile UE 501 may represent any of a variety of devicessuch as a server, a desktop computer, a laptop computer, a cellularphone, a Personal Digital Assistant (PDA), a smart phone or otherelectronic devices. In some embodiments, the electronic mobile UE 501communicates with eNodeB 502 based on a LTE or Evolved UniversalTerrestrial Radio Access (E-UTRA) protocol. Alternatively, anothercommunication protocol now known or later developed can be used.

Mobile UE 501 comprises a processor 503 coupled to a memory 504 and atransceiver 505. The memory 504 stores (software) applications 506 forexecution by the processor 503. The applications could comprise anyknown or future application useful for individuals or organizations.These applications could be categorized as operating systems (OS),device drivers, databases, multimedia tools, presentation tools,Internet browsers, emailers, Voice-Over-Internet Protocol (VOIP) tools,file browsers, firewalls, instant messaging, finance tools, games, wordprocessors or other categories. Regardless of the exact nature of theapplications, at least some of the applications may direct the mobile UE501 to transmit UL signals to eNodeB (base station) 502 periodically orcontinuously via the transceiver 505.

Transceiver 505 includes uplink logic which may be implemented byexecution of instructions that control the operation of the transceiver.Some of these instructions may be stored in memory 504 and executed whenneeded by processor 503. As would be understood by one of skill in theart, the components of the uplink logic may involve the physical (PHY)layer and/or the Media Access Control (MAC) layer of the transceiver505. Transceiver 505 includes one or more receivers 507 and one or moretransmitters 508.

Processor 503 may send or receive data to various input/output devices509. A subscriber identity module (SIM) card stores and retrievesinformation used for making calls via the cellular system. Processor 503may send information to a display unit for interaction with a user ofmobile UE 501 during a call process. The display may also displaypictures received from the network, from a local camera, or from othersources such as a Universal Serial Bus (USB) connector. Processor 503may also send a video stream to the display that is received fromvarious sources such as the cellular network via RF transceiver 505 orthe camera.

Mobile UE 501 also includes an ISM band transceiver 518 that is used tocommunicate with other devices over channels assigned in the ISM bandusing standards or protocols adapted for the ISM band, such asBluetooth, WiFi, or ZigBee. ISM band transceiver 518 provides channelinformation to processor 503, which in turn generates CQI reports fortransmission to eNodeB 502 via LTE transmitter 505.

In one embodiment, UE 501 receives interference parameters from basestation 502. Processor 503 uses the interference parameters to identifyand suppress interference signals received at receiver 507.

eNodeB 502 comprises a processor 510 coupled to a memory 511, symbolprocessing circuitry 512, and a transceiver 513 via backplane bus 514.The memory stores applications 515 for execution by processor 510. Theapplications could comprise any known or future application useful formanaging wireless communications. At least some of the applications 515may direct eNodeB 502 to manage transmissions to or from mobile UE 501.

Transceiver 513 comprises an uplink resource manager, which enableseNodeB 502 to selectively allocate uplink PUSCH resources to mobile UE501. As would be understood by one of skill in the art, the componentsof the uplink resource manager may involve the physical (PHY) layerand/or the Media Access Control (MAC) layer of the transceiver 513.Transceiver 513 includes at least one receiver 515 for receivingtransmissions from various UEs within range of eNodeB 502 and at leastone transmitter 516 for transmitting data and control information to thevarious UEs within range of eNodeB 502. Symbol processing circuitry 512performs demodulation using known techniques. Random access signals aredemodulated in symbol processing circuitry 512.

The uplink resource manager executes instructions that control theoperation of transceiver 513. Some of these instructions may be locatedin memory 511 and executed when needed on processor 510. The resourcemanager controls the transmission resources allocated to each UE 501served by eNodeB 502 and broadcasts control information via the PDCCH.UE 501 may receive TTD UL/DL configuration instructions from eNodeB 502.

FIG. 6 is a flowchart illustrating a method for using channel qualityreports to reduce inter-band interference according to one embodiment.In step 601, channel information is received at a first wirelesscommunication device from a second wireless communication device. Thefirst wireless device is operating in a first frequency range, and thesecond wireless device is operating in a second frequency range. Thefirst frequency range is adjacent to the second frequency range. In step602, a channel quality report is generated at the first wirelesscommunication device. The channel quality report indicates thatparticular sub-bands in the first frequency range have low channelquality. The particular sub-bands are selected using the channelinformation.

In one embodiment, the channel information is an operating channelassigned to the second wireless communication device. The particularsub-bands may be selected because transmissions in the sub-bands woulddegrade communications or cause interference in the operating channel.

The first wireless communication device may be, for example, an LTE UE,and the second wireless communication device operates in the ISMfrequency range. The second wireless communication device may complywith the Bluetooth standard, an IEEE 802.11 standard, an IEEE 802.15standard, and the ZigBee standard.

In one embodiment, the first wireless communication device and thesecond wireless communication device are different circuits within asingle UE device.

A system for using channel quality reports to reduce inter-bandinterference comprises a first wireless communication circuit configuredto operate in a first frequency range according to a first standard, anda second wireless communication circuit configured to operate in asecond frequency range according to a second standard. The firstfrequency range is adjacent to the second frequency range. The systemalso comprises a controller configured to generate a channel qualityreport according to the first standard. The channel quality reportindicates that particular sub-bands in the first frequency range havelow channel quality, where the particular sub-bands are selected usingchannel information received from the second wireless communicationdevice.

The channel information may identify an operating band assigned to thesecond wireless communication circuit. The sub-bands may be selectedbecause transmissions in the particular sub-bands would degradecommunications in the operating band.

The first standard may be an LTE wireless communication standard, andthe channel quality report may be an LTE CQI report. The second standardmay be one of the Bluetooth standard, an IEEE 802.11 standard, an IEEE802.15 standard, and the ZigBee standard. The second frequency range maybe the ISM band.

The first and second wireless communication circuits may be componentsof the same UE device. Alternatively, the first and second wirelesscommunication circuits may be components of the different UE devices.The system may include a communication link between the first and secondwireless communication circuits, wherein the communication link isadapted to pass channel information.

A UE according to one embodiment may comprise an LTE communicationcircuit, an ISM band communication circuit, and a controller configuredto generate LTE Channel Quality Indication (CQI) reports, wherein thecontent of the CQI reports is selected using channel informationassociated with an ISM band channel assigned to the ISM bandcommunication circuit. The CQI reports may intentionally misidentifypoor channel quality in selected LTE sub-bands because transmissions inthe selected sub-bands would degrade communications in the assigned ISMband channel.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this invention pertains havingthe benefit of the teachings presented in the foregoing descriptions,and the associated drawings. Therefore, it is to be understood that theinvention is not to be limited to the specific embodiments disclosed.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

What is claimed is:
 1. A method, comprising: receiving, at a firstwireless communication device operating in a first frequency band,channel information from a second wireless communication deviceoperating in a second frequency band, wherein the first frequency bandis adjacent to the second frequency band; generating a channel qualityreport at the first wireless communication device, the channel qualityreport indicating that particular sub-bands in the first frequency bandhave low channel quality, wherein the particular sub-bands are selectedusing the channel information; and receiving, at the first wirelesscommunication device, a sub-band assignment within the first frequencyband.
 2. The method of claim 1, wherein the channel informationcomprises an operating channel assigned to the second wirelesscommunication device.
 3. The method of claim 2, wherein the particularsub-bands are selected because transmissions in the sub-bands woulddegrade communications in the operating channel.
 4. The method of claim1, wherein the particular sub-bands are selected because transmissionsin the sub-bands would cause interference in the operating channel. 5.The method of claim 1, wherein the first wireless communication deviceis a Long Term Evolution (LTE) user equipment (UE), and the secondwireless communication device operates in an Industrial, Scientific andMedical (ISM) frequency band.
 6. The method of claim 1, wherein thefirst wireless communication device is a Long Term Evolution (LTE) userequipment (UE), and the second wireless communication device operates inan unlicensed frequency band.
 7. The method of claim 5, wherein thesecond wireless communication device complies with a standard selectedfrom the group consisting of a Bluetooth standard, an IEEE 802.11standard, an IEEE 802.15 standard, and a ZigBee standard.
 8. The methodof claim 1, wherein the first wireless communication device and thesecond wireless communication device are different circuits within auser equipment (UE) device.
 9. A system, comprising: a first wirelesscommunication circuit configured to operate in a first frequency bandaccording to a first standard; a second wireless communication circuitconfigured to operate in a second frequency band according to a secondstandard, wherein the first frequency band is adjacent to the secondfrequency band; and a controller configured to generate a channelquality report according to the first standard, the channel qualityreport indicating that particular sub-bands in the first frequency bandhave low channel quality, wherein the particular sub-bands are selectedusing channel information received from the second wirelesscommunication circuit, the controller further configured to receive asub-band assignment within the first frequency band.
 10. The system ofclaim 9, wherein the channel information identifies an operating bandassigned to the second wireless communication circuit.
 11. The system ofclaim 10, wherein the sub-bands are selected because transmissions inthe particular sub-bands would degrade communications in the operatingband.
 12. The system of claim 9, wherein the first standard is a LongTerm Evolution (LTE) wireless communication standard, and the secondstandard is selected from the group consisting of a Bluetooth standard,an IEEE 802.11 standard, an IEEE 802.15 standard, and a ZigBee standard.13. The system of claim 9, wherein the second frequency band is anIndustrial, Scientific and Medical (ISM) band.
 14. The system of claim9, wherein the second frequency band is an unlicensed frequency band.15. The system of claim 9, wherein the channel quality report is a LongTerm Evolution (LTE) Channel Quality Indication (CQI) report.
 16. Thesystem of claim 9, wherein the first wireless communication circuit andthe second wireless communication circuit are components of the sameuser equipment (UE) device.
 17. The system of claim 9, wherein the firstwireless communication circuit and the second wireless communicationcircuit are components of the different user equipment (UE) devices. 18.The system of claim 17, further comprising: a communication link betweenthe first wireless communication circuit and the second wirelesscommunication circuit, the communication link adapted to pass channelinformation from the second wireless communication circuit to the firstwireless communication circuit.